The role of groundwater during drought

Abstract

Groundwater drought is a natural hazard that develops when groundwater systems are affected by drought, first groundwater recharge and later groundwater levels and groundwater discharge, that decreases. The origin of drought is a deficit in rain precipitation and that takes place in all the elements that comprise the hydrological cycle (flow in the rivers, soil humidity and groundwater). Depending on the deficit and duration of the drought this may affect all segments or not. This chapter analyses how drought influences and affects groundwater, which depends not only on the rain deficit but on some other parameters such as the physical properties of the aquifer, type of porous rock, aquifer dimensions and thickness of the unsaturated zone. Hydrological drought can be analysed using hydro-geological features and parameters such as piezometer levels, natural recharge or base flow. The usefulness of some indexes is presented here. The related concepts of water scarcity, overexploitation and groundwater mining are explained. This chapter reviews the importance and dependence of the different countries of the Mediterranean Basin on groundwater.